Apparatus for forming a blown plastic container

ABSTRACT

A method and apparatus are disclosed for forming a plastic container by a blow molding operation. In the method, a tubular thermoplastic parison is blown to a preform within a first mold by a blow pipe inserted into one axial open end of the parison. Prior to removing the preform from the first mold, a secondary opening is formed in the wall of the preform, either by a spike-shaped piercing surface over which the parison is expanded or by a vent port through which blow air is exhausted to rupture an opening in the preform wall. The preform is then transferred to a second mold, which pinches shut the initial blowing opening of the preform. A second blow pin is inserted into the secondary opening to supply blow air under pressure to expand the preform to a container. The secondary opening may be formed into a finish opening on the container during the second blow molding operation, thus enabling the finish opening to be located at a position remote from the position on the container which corresponds to an axial extremity on the original tubular parison.

This is a division of application Ser. No. 735,554, filed on Oct. 26,1976 now U.S. Pat. No. 4,070,429.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to a method and apparatus forforming a blown thermoplastic container, and more specifically in oneembodiment to a "blow-and-blow" operation where a secondary opening isformed in a preform during the first blowing operation and then blow airis introduced through the secondary opening in the final blowingoperation.

General blow molding techniques are well-established in the prior art,including both "single-blow" operations and "blow-and-blow" operations.An example of the "blow-and-blow" operation is disclosed in the U.S.Pat. No. 3,767,747, which is incorporated by reference.

One method of forming a blown plastic article according to the prior artincludes inserting a blow pipe into one end of a parison which isenclosed within a blow mold cavity. Blow air under pressure is thenintroduced into the parison through the blow pipe to inflate the parisoninto the configuration of the desired article. This results in a blownarticle having an opening generally at the center of one of its axialends.

When it has been desireable to form an opening in a blown plasticarticle at a position which corresponds to something other than an axialextremity of the article, it has been the general practice in the priorart to cut and trim the article in an operation subsequent to blowmolding. This, obviously, presents the problems and disadvantages ofadditional and undesirable handling, equipment, time and expense.

SUMMARY OF THE INVENTION

The present invention over comes the prior art problems by a method andapparatus whereby an opening may be formed at an intermediate positionof the article during the blow molding operation.

In one aspect of the disclosed method, a blowable plastic shape, such asa parison or preform, is enclosed within a blow mold cavity by theclosure of the sections of a blow mold. Next, pressurized blow air isintroduced into the plastic shape to form the blown plastic article.While the blown plastic article is within the blow mold cavity, anopening is formed in its side wall portion. This may be achieved, in oneembodiment, by expanding the blowable shape during the blow moldingoperation against a prong-shaped piercing surface. In a second disclosedembodiment, the blow mold includes a vent port which is closed toatmosphere during the blowing operation. Immediately after the blowingoperation, the vent port is exposed to atmosphere, permitting thepressurized blow air within the blown article to rupture a portion ofthe blown article and form the desired opening.

The disclosed method is also advantageously employed in a"blow-and-blow" operation. In this aspect of the invention, blow airunder pressure is introduced into a tubular thermoplastic parison toexpand the parison to a preform configuration. Next, an opening isformed in the wall of the preform at a position other than that wherethe air under pressure is introduced. The preform with the formedopening is then enclosed within a blow mold cavity, where additionalblow air is introduced through the formed opening to expand the preforminto a final article. In a more limited aspect, the originalintroduction of blow air into the parison is by way of a blow pininserted into an opening at one axial parison extremity, which ispinched shut when the preform is placed within the blow mold cavity.

A very specific application for this invention is for forming a finishopening in a blown container, where the finish opening is positioned ata side of the container, or off-center at the top of the container. Theresultant freedom of container design will be appreciated, since it isno longer necessary to blow twice through the same blowing opening. Inorder to assure that the finish opening is not unduly thinned, theregion in the preform which circumscribes the formed opening may beformed with a concave configuration that is thicker than the surroundingblown preform wall portions. The concave region is then blown into thefinish forming cavity in the final blow mold, having a thicknesssubstantially the same as that portion of the article immediatelyadjacent the finish formation.

In an alternative embodiment, the method may be utilized to form aplurality of blown containers. In this embodiment, the preform is blownwithin a first blow mold cavity having a plurality of side by side,interconnected primary cavities. The blown preform is then transferredto a final molding station, where portions of the blown preform arepinched together for the formation of the plurality of containers.

In another disclosed embodiment, the blown preform and final articlehave a configuration of an elongated capsule-shape with an intermediate,radially outwardly directed annular plastic ring. After the final blowmolding step, a portion of the annular plastic ring is cut off, leavingtwo separate containers formed from one single plastic parison.

Accordingly, the present invention provides at least the followingadvantages: (1) the ability to easily, efficiently, and cheaply formopenings in blown containers at off-centered positions relative to theaxial extremity of the plastic article; (2) the elimination of cuttingand trimming operations separate and apart from the blow moldingoperation; (3) the ability to form openings in the side wall of acontainer, without sacrifices in cycle time; and (4) the capability offorming containers of unusual shapes, as where the dispensing opening islocated off-center, etc.

Other meritorious features and advantages will become apparent from thefollowing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front elevational view of a preform blow mold.

FIG. 2 is a schematic side elevational view taken along plane 2--2 ofFIG. 1, illustrating a piercing mechanism for forming an opening in ablown preform according to the present invention.

FIG. 3 is a schematic view taken along plane 3--3, as indicated in FIG.2.

FIG. 4 is a schematic front elevational view of a final blow moldingcavity where the preform is blown to the configuration of the finalarticle.

FIG. 5 is a schematic side elevational view taken along plane 5--5 ofFIG. 4, illustrating the manner of inserting a blow pin within theopening formed in the preform during the preform molding operation.

FIG. 6 is a schematic view taken along plane 6--6 of FIG. 5.

FIG. 7 is a schematic side elevational view of a preform mold in asecond embodiment of the disclosed invention.

FIG. 8 is a schematic view taken along plane 8--8 as indicated in FIG.7.

FIG. 9 is a schematic side elevational view of a final blow moldingcavity of the second embodiment.

FIG. 10 is a schematic view taken along plane 10--10, as indicated inFIG. 9, again indicating the manner of inserting a blow pin in anopening formed in the preform.

FIG. 11 is a schematic side elevational view of a third disclosedembodiment, illustrating a preform mold.

FIG. 12 is a fragmented side elevational view of the opening formingoperation in the preform mold shown in FIG. 11.

FIG. 13 is a schematic side elevational view of a final blow mold of thethird embodiment.

FIG. 14 is a schematic side elevational view of a die cutting operationused in conjunction with the third embodiment to form two "wide-mouth"containers from the single blown container.

FIG. 15 is a schematic side elevational view similar to FIG. 14, andillustrating the terminal phases of the die cutting operation.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

The present disclosure relates to a method and apparatus for formingopenings in the side wall of blown plastic containers. Three separateembodiments are disclosed in FIGS. 1-6, FIGS. 7-10 and FIGS. 11-15.

THE EMBODIMENT OF FIGS. 1-6

Referring to FIGS. 1-3, a blowable thermoplastic parison 20 isillustrated as enclosed within a blow mold cavity 22 defined by a pairof blow mold sections 24 and 26. The parison may be formed byconventional free extrusion or injection molding, techniques, theillustrated parison 20 being of the free-extrusion type and thereforemold sections 24 and 26 have pinched the parison shut at its bottom toform a tail 20. Conventional tail pullers (not shown) may be utilized atthe preform molding station to remove the tail 28 from the remainder ofthe plastic material while mold halves 24 and 26 are shut.

An axially reciprocable and laterally moveable blow and transfer pin 30is received within a concave region 32 cooperatively defined by the twopreform mold halves 24 and 26. The blow pin includes an annular groove34, which receives waste plastic material to enable a blown preform tobe conveyed on the pin 30. An axial air supply port extends through blowpin 30 and is interconnected with a supply of blow air under pressure.Additionally, the supply port 36 is in axial alignment with an opening38 defined by the blow mold halves, opening 38 communicating with theinterior of the blow mold cavity to facilitate the introduction ofpressurized blow air into parison 20.

To form an opening in the side wall of the preform, a piercing mechanismis secured to one of the blow mold halves and includes an axiallyreciprocable rupture pin 40, having a spike 43 circumscribed by aconvex, domed surface 42. The axial reciprocal movement of the rupturepin 40 is effected by a hydraulic cylinder 48 which houses a piston 44that is interconnected to the rupture pin 40 by a piston rod 46.

The molding operation at the preform mold station is carried out asfollows: First, a blowable thermoplastic parison 20 is positioned, forexample by downward extrusion, between the open blow mold sections 24and 26, which are then closed on the parison to pinch shut the parisonbottom. Next, blow pin 30 is axially moved downwardly into the positionas shown in FIGS. 1 and 2, pinching an upper portion of the parison toforce plastic material into groove 34. Prior to the actual blow moldingoperation, the rupture pin is moved to the position as illustrated inFIG. 2. Blow air under pressure, for example at about 100 PSI, is thenintroduced through port 36 and an opening 49 in the plastic material toradially inflate the parison outwardly into engagement with the moldwall surfaces, forming a preform 50. During expansion of the plasticmaterial, a portion of the parison is expanded onto spike 43, forming anopening 52 in the preform. The material circumscribing the opening 52expands onto the convex surface 42 to form a concave preform portion 54.This concave section is thicker and hotter than the immediatelysurrounding preform portions, in accordance with Applicant's pendingapplication Ser. No. 566,016 now U.S. Pat. No. 3,989,784, incorporatedby reference.

After the blowing operation, rupture pin 40 is retracted by cylinder 48to provide clearance for removal of the preform from the mold. Next,mold halves 24 and 26 are opened, by conventional hydraulic means (notshown), leaving the preform suspended from blow pipe 30 by the wastematerial extending into the annular groove 34.

Next, the blow pipe 30 is laterally displaced to a subsequent moldingstation, which is illustrated by FIG. 4-6. The mold at the subsequent orfinal blow molding station is comprised of mold halves 60 and 62, whichcooperatively define an internal blow mold cavity 64. The mold halvesinclude pinching surfaces 66 and 68 which register with the opening 49in the preform to pinch that opening shut, as illustrated. Additionally,the mold halves include pinching surfaces 70 and 72 which cooperate todefine a recess 74 to form a handle in the final article.

Referring more specifically to FIG. 5, an axially reciprocal blow pin 80is illustrated in co-axial arrangement with a finish defining cavityregion 76 of the blow mold. An air delivery port 82 extends through theblow pin 80 to supply pressurized blow air through preform opening 52 toinflate the preform into the final container 86.

The method at the final molding station includes, first, closing moldsections 60 and 62 onto the preform 50 which is suspended from blow pipe30. Closure of the molds results in (1) pinching preform opening 49 shutby pinching surfaces 66 and 68 and (2) pinching an upper portion of thepreform shut by surfaces 70 and 72 to form a handle opening for thefinal container. Next, the axially reciprocal blow pin is inserted intothe preform opening 52 for the delivery of blow air under pressure intothe preform. The blowing operation results in an expansion of thepreform into the final container configuration 86, and includesexpanding concave preform region 54 outwardly into convex finish region76 to form a finish 84. In accordance with the invention, the finishportion 84 has a thickness substantially the same as the immediatelyadjacent, surrounding preform portions, as more fully explained inApplicant's copending application, Ser. No. 566,016 now U.S. Pat. No.3,989,784. Additionally the blowing operation at the second blow moldmay be practiced to achieve molecular orientation of the plasticmaterial, as more fully set forth in Applicant's U.S. Pat. No.3,767,747, incorporated by reference.

Subsequent to the blow molding operation, the axially reciprocal blowpin 80 is displaced from the mold halves, which are then opened, leavingthe blown container 86 suspended from blow pipe 30. The blow pipe canthen be displaced to an unloading station, where the container isseparated from the waste plastic material. Then, the blow pin will belaterally conveyed back into alignment with a preform mold cavity forthe subsequent formation of another blown container.

THE EMBODIMENT OF FIG. 7-10

Referring to FIGS. 7 and 8, an elongated tubular thermoplastic parison100 is illustrated in a mold cavity defined by preform mold halfsections 102 and 104, including pinching surfaces 108 and 110 which haveformed a tail 106 on the parison. A blow pipe 112 is illustrated asbeing positioned within a concave region 114 defined by the mold halves,the blow pipe including an air delivery port 116 and an annular groove118 to receive waste material.

A mold cavity cooperatively defined by the mold halves 102 and 104includes a plurality of elongated major cavities 120, generally takingthe form of a container and being spaced by opposed flats or lands 122.FIG. 8 illustrates that an axially reciprocable rupture pin 130 isprovided for each major cavity 122, the rupture pin including a convexdome-shaped surface 132 and a piercing point 134. In the same manner asdiscussed in regard to the embodiment of FIGS. 1-6, the each rupture pinis reciprocated by a hydraulic cylinder 136.

The operation at the molding station of FIGS. 7 and 8 includes, first,positioning a parison 100 between opened mold sections, 102 and 104which are then closed onto the parison. Blow pin 112 is thenreciprocated downwardly into the open end 114 of the parison to commencethe blow molding operation. Pressurized blow air is delivered into theparison by way of air delivery port 116 and through opening 139 in theplastic parison, causing the plastic material to expand (1) to form aplurality of preform segments 140 destined to form the individual finalcontainers, (2) to form plastic bridging segments 142, interconnectingsegments 140, (3) to cause plastic material to expand onto and overpiercing points 134 of the rupture pins, forming openings 146, and (4)to form concave preform segments 144 on the convex surface 132 of therupture pins.

After blowing, the rupture pins 130 are retracted by hydraulic cylinders136 and blow mold halves 102 and 104 are separated by conventionalhydraulic means (not shown) leaving the blown preform suspended fromblow pipe 112.

The blow pipe with suspended preform is then displaced to a finalmolding station illustrated by FIGS. 9 and 10, where a final mold iscomprised of section halves 150 and 152 which include pinching surfaces154 and 156 to engage and close the opening 139 in the preform. The moldhalves cooperatively define separate container cavities 158 which areseparated by opposed pairs of pinching surfaces 160, 162, 164 and 166,which engage and seal the preform bridge sections 142 during moldclosure.

FIG. 10 illustrates that an axially reciprocable blow pin 170 isprovided for each mold cavity 158. These blow pins are in registry witheach of the openings 146 in the preform in a manner similar to that ofthe embodiment in FIGS. 1-6.

The method of operation at the final blow mold includes, first, closingthe mold halves 150 and 152 onto the preform. During mold closure,pinching surfaces 154 and 156 close previously existing opening 139 inthe preform; and the opposed pairs of pinching surfaces 160-162 and164-166 engage preform bridge segments 142 to pinch shut and weld theplastic material together for the formation of individual containers.

After mold closure, blow pins 170 are displaced to the positionillustrated in FIG. 10. The introduction of blow air through the blowpins expands the preform segments 142 into individual containers 172including finish 174 formed from concave preform region 144. Asdiscussed in connection with the embodiment of FIGS. 1-6, finish 174will be substantially as thick as the surrounding nonconvex containerportions. After blowing, blow pins 170 are retracted and blow moldhalves 150 and 512 are opened, leaving the tandem, attached containers172 suspended from blow pin 112. The individual containers may then beseparated along the pinched lines or utilized in combination, asdesired.

THE EMBODIMENT OF FIGS. 11-15

The embodiment disclosed in these figures relates to a combination formaking two "wide mouth" containers from a single plastic parison.

In FIG. 11, a parison 200 is illustrated in a blow mold cavity 202 whichis defined by closed preform mold halves 204 and 206. The mold cavityincludes an annular concave ring portion 216 to form a correspondinglyshaped configuration on the preform. An axially reciprocable blow pipe210 including an air supply port 212 registers with a mold opening 214for the supply of blow air.

In this embodiment, an alternative means is disclosed for forming anopening in the side wall of the preform. This alternative means includesa vent port 218 which may be opened and closed to atmosphere by way of atwo position valve 220, including a closed branch line 222 and a throughor open branch line 224.

The blow molding operation at the position of FIG. 11 proceeds asfollows. First, the blow mold halves 204 and 206 are closed on parison200, pinching shut the bottom of the parison and forming an opening 226at the top of the parison. The axially reciprocable blow pipe 210 isthen lowered into position in alignment with mold opening 214.Immediately subsequent to lowering of the blow pipe 210, blow air underpressure is delivered through port 212 and through preform openign 226to inflate the parison into the configuration of mold cavity 202. Duringthe blow molding operation, valve 220 is positioned as illustrated inFIG. 11 to prevent escape of any blow air. Accordingly, preform plasticmaterial covers vent port 218.

After blowing, but while the preform is pressurized by the blow air,valve 220 is switched to the position as illustrated in FIG. 12. Thatis, through branch line 224 is placed "in-line" with vent port 218,which is thereby placed in communication with atmosphere. As a result,the pressurized fluid inside the preform ruptures the plastic materialat vent 218 to form an opening 230, and the pressurized fluid escapesthrough vent port 218 and through line 224 to atmosphere.

Subsequently, the blow mold halves 204 and 206 are opened and preform228 is conveyed by blow pin 210 to a final blow molding station,illustrated by FIG. 13. The final blow mold is comprised of moldsections 240 and 242, which includes pinching surfaces 244 and 246 toengage and shut preform opening 226. A blow pin 248 may be rigidlyconnected to mold half 240 for registry with preform opening 230. Aftersupplying blow air under pressure through blow pin 248 to form the finalcontainer 250, mold halves 240 and 242 are opened and the article 250 isplaced within a shearing die 260, illustrated by FIGS. 14 and 15. Theshearing die is comprised of upper and lower relatively moveable,annular die sections 262 and 264, respectively, as more fully disclosedin U.S. Pat. No. 3,711,233, incorporated by reference. The upper diesection 262 includes an annular shearing edge 266, which severs theradially outward ring on article 250, as illustrated in FIG. 15, to formtwo wide mouth containers 270 and 272, such a beakers.

It is to be understood that the foregoing description of the presentinvention is exemplary in nature, rather than limiting. For example, thealternative opening forming means shown in FIGS. 11 and 12 may be usedin conjunction with a convex forming surface as discussed in connectionwith the embodiments of FIGS. 1-10. Additionally, the piercing pinsshown in the embodiment of FIGS. 7-10 may be placed other than along themold parting line. For example, the pins could be placed on the side ofthe mold parallel to the axis of reciprocation eliminating therequirement for separate hydraulic reciprocation equipment since thepiercing pins would reciprocate with the mold.

I claim:
 1. In a molding apparatus having blow mold sections whichcooperate to define a blow mold cavity in which a parison is blown toform a blown plastic article, the improvement of means associated withsaid mold for forming a opening in the blown article, said meanscomprising an opening in one of said mold sections connecting the moldcavity with the atmosphere, valve means for selectively opening andclosing the opening, and means independent of said opening forintroducing air into a parison confined in said cavity, said valve means(a) closing the port during the introduction of air under pressureduring a blow molding operation to form the blow plastic article and (b)opening the port to atmosphere subsequent to the blow molding operationso that the air under pressure within the blown article ruptures thatportion of the article overlying the port and vents through the port toatmosphere.
 2. In a blow molding assembly having first and second blowmolds, the first blow mold including a cavity to form a blown preformfrom a blowable plastic parison, and the second mold including a cavityto form a blown plastic container from a preform, the preform beinglarger than the parison and the container being larger than the preform,the improvement of:(1) said first blow mold including first blow pinmeans for introducing pressurized blow air into the parison through afirst parison opening to form the blown preform, and means for forming asecond opening in the blown preform at a position spaced from said firstopening; and (2) the second blow mold including pinching surface meansto pinch shut the first opening in the blown preform, and second blowpin means registering with said second preform opening for introducingpressurized blow air into the preform to form the blown plasticcontainer having only the second opening.
 3. A blow molding apparatus,including:(1) a first blow mold means having a preform cavity to receivean elongated blowable plastic parison having a first opening at oneaxial extremity thereof, means for supplying blow air through said firstopening to form a blown plastic preform in said cavity, means defining aconvex molding surface in said preform mold cavity for forming a concaveportion on the preform during blowing, and means for forming a secondopening through the wall of said concave portion; and (2) a second blowmold having a second cavity to receive a blown preform from the firstblow mold to form a blown container, means defining a finish formingconcave region in said second cavity to form a convex finish portion onthe blown container from the concave preform portion, blow pin meansextending coaxially of said finish forming cavity region and into thesecond opening in the concave preform portion, and means in said secondcavity including pinching surfaces to engage and close said extremityopening on the blown preform.
 4. The apparatus as defind in claim 3,characterized by said second opening forming means including a sharppiercing surface on said convex molding surface.
 5. The apparatus asdefined in claim 3, characterized by said second opening forming meansincluding a port for selectively exposing a section of the concavepreform portion to atmospheric pressure, so that the blow air underpressure within the preform will rupture that section at the preform. 6.An apparatus for forming a plurality of blown containers from a singletubular parison of thermoplastic materials, comprising:a pre-form moldmeans having a plurality of interconnected, major, elongated cavitiesgenerally perpendicular to the longitudinal axis of the parison; a firstblowing means for introducing blow air under pressure into the parisonthrough an opening at one axial parison extremity and forming a pre-formby expanding the parison into the major cavities and against moldportions interconnecting those cavities, forming a plurality of pre-formsegments interconnected by integral, opposed pairs of joining portions;means associated with each major elongated cavity for forming an openingin the wall of each pre-form segment during expansion of the parison;destined to form an individual container a final blow mold including (a)first pinching means to pinch shut said opening at the one axial parisonextremity, (b) a plurality of second pinching means to pinch shut andweld together portions of the corresponding, opposed joining portionsand (c) a plurality of individually cavities enclosing each of thepre-form segments within an individual blow cavity; and a plurality ofsecond blow pin means associated with each individual cavity of thefinal blow mold and means for inserting each second blow pin meansthrough the opening in the wall of each corresponding pre-form segmentfor introducing blow air under pressure into each pre-form segment toform a plurality of individual blown containers.